Efficient Simulation of Two-Phase Compositional Flow in Fractured Reservoirs Using 3D Unstructured Gridding in Complex Geometries

Abstract

We present a higher-order numerical model for compositional two-phase flow in fractured media in 2D and in 3D unstructured gridding. The model accommodates all types of finite elements; in particular, quadrangular and triangular elements in 2D, and hexahedra, prisms and tetrahedra elements in 3D. We apply for the first time the fracture cross-flow equilibrium (FCFE) concept in compositional two-phase flow in 3D. FCFE is combined with the hybridized form of the mass conservative mixed finite element (MFE) and the higher-order discontinuous Galerkin (DG) method. We have developed an interface that connects computer-aided-design (CAD) software to the mesh generator. The interface enables us to generate the most complicated fracture shapes. The application is intended for fracking simulation. To the best of our knowledge the complexity of fractures that we generate/simulate is not reported in the past. Our algorithm allows flow simulation in fractures in all range of permeability values as opposed to other models where low permeable fractures affect the accuracy of the results. We demonstrate the efficiency, accuracy, and strengths of our model in comparison to alternatives including the embedded discrete fracture approach in different examples. This work covers generation and simulation of two-phase compositional flow in complex fractured media in 3D unstructured gridding.